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The mining industry, both here and internationally, is continually developing increasingly sophisticated software to compute mineral resource estimates, but these processes cannot compensate for a flawed geological interpretation of the geology of the economic commodity(s) concentrations. Quality assurance and quality control (QA/QC) is becoming increasingly common in association with the sampling and assaying practices within the industry. However, it is rare in the case of a geological interpretation associated with mineral resource estimation. Why? In the context of this paper, QA/QC relates to the use of statistical and graphical tools to show that the geological economic commodity concentrations have been appropriately domained. Domaining is essential to improve the chance of getting a mineral resource estimate right. Commodity value and acceptable concentration variation within a mineral resource can be ingredients that make mineral resource estimation difficult to get right. But it is possible to get it right a very high proportion of the time. It is more likely to occur when inappropriate data consolidation is minimised. In any case, inappropriate data consolidation is significantly reduced when the geological interpretation is strongly consistent with the data and it is demonstrable. To achieve quality global estimates of geological domain concentrations, it is essential that the geology of the prospect is understood sufficiently that the deposit is appropriately domained. Appropriate domaining occurs when sample populations are separated in such a way that only data in harmony with each other within the population contributes to the domainÆs concentration estimate. The paper will use four brief case studies to illustrate how QA/QC can be used to display data and validate the underpinning geological interpretation through its associated domaining to get it right when it comes to a mineral resource estimation.

Jan 1, 2007

By K George

The Dugald River lead-zinc-silver deposit is located approximately 60 km north-west of Cloncurry and 87 km north-east of Mount Isa. The development project is expected to turn operational in 2018. The resource is estimated to contain 61.1 Mt at 12.6 per cent zinc, 1.9 per cent lead and 34 g/t silver, with a projected mine life of 25 years. The evolution from exploration project to development project has presented multiple challenges for the technical team. Understanding and modelling the structural complexity of the deposit has been one of these challenges.Historically fault zones were logged as a lithology, with structural measurements recorded in a separate database table. When underground drill programs and development commenced in late 2012, it was recognised the deposit was more structurally complex than had been modelled. The extensive number of fault zone lithologies in core logging, made it difficult to identify fault trends and model faults in 3D software packages.In 2014, a structural project was conducted to produce a fault model for the deposit. The project highlighted that by logging the faults as a lithology, a shortage of fault characteristics was being recorded. Additionally, structural information could not be filtered to identify different fault sets due to the lack of information available to filter on. One of the major outcomes of the study was to change the methodology for the structural logging of drill core.Faults are now logged in a separate structural log. The structural log collects two types of information: interval data and point data. The interval data represents the damage zone of the fault in the surrounding rock and the point data the plane of movement for the fault. The faults are further characterised by their intensity on a scale of one to five, the type of fault structure (fault breccia, fault vein etc), the minerals present on the fault surface and structural measurements when available.The new data set allows fault data to be filtered based on fault characteristics, making implicit and explicit modelling of the faults more timely and accurate. The data set can be used to produce fault wireframes as single surfaces from the point data or hanging wall and footwall surfaces from the interval data. The logging method and how its applied in fault modelling form the focus of this paper.CITATION:George, K, 2017. A new approach to logging and modelling faults at the Dugald River Pb-Zn-Ag deposit, North West Queensland, in Proceedings Tenth International Mining Geology Conference 2017, pp 315–320 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By T N. Little

This paper is concerned with the influence of engineering geology on design of Wall Control Blasts. In the Introduction, the Blast Management Framework and the Blast Design Requirements classification system (previously developed by the author) is drawn upon to set the context. Blasting objective for all wall control blasts involves both profile and damage control. Four classes of approaches for blast design are outlined and briefly discussed. Five distinct wall control blasting techniques are summarised. The general relationship between geology and blast design is explored in the paper. Influence of geology on pre-split and post-split design and blasting direction is highlighted. Wall damage modelling from the closest row of blastholes is also introduced using the Analytical Damage Model (ADM). The relationship of rock properties and explosive selection and in particular the Mach wave generation is introduced to assist blast designer in this regard. Finally a Conceptual Model that relates vibration, damage and rock mass condition has been presented along with some applications that have been undertaken by the developer. Eight conclusions have been formulated based on extensive work in this area and the current study.

Jun 22, 2022

By D La Rosa, D Bennett

"Exploration drill core provides for a number of standard measurements essential for determining the viability of a new mine or the extension of an existing one. Rock lithology and alteration can be visually determined and grade measured from the half core. Geotechnical parameters such as rock strength and structure can also be measured. Using suitable proxies, these metrics can then be used to estimate run-of-mine (ROM) particle size. In combination with comminution test results, these can subsequently be used to design comminution circuit configurations and estimate their performance.The Frieda River Project drill core for the large Horse-Ivaal-Trukai copper-gold porphyry deposit was unusual due to a late stage gypsum-anhydrite stockwork event that overprinted much of the deposit. Above the base of the oxidised zone, which closely matches the water table, gypsum and anhydrite has been leached out, effectively removing the glue holding the rock mass together. As a result, much of the rock above this gypsum-anhydrite surface is fragmented and gravel-like in texture, while the material below this horizon is typically uniform and competent.Large volumes of the orebody above the gypsum-anhydrite surface are expected to need minimal or no blasting for efficient excavation. In addition, the fragmented nature of much of the material was expected to reduce comminution specific energy as it already appears as though it has been crushed. While this was expected to have positive impacts to the operation, the lack of standard geological logging methods available to accurately define the degree of in situ fragmentation led to difficulty in gaining certainty over the ROM product and grinding circuit feed size distributions.Using the extensive library of core photos for the project, a novel method using image analysis techniques to take both the intact core and gravel into account to predict ROM fragmentation was developed. In addition, existing point load test data was used to infer the strength of the rock and its impact on the blasting, crushing and grinding processes. The novel approach allowed development of ROM size distribution data and improved certainty in the results of comminution circuit designs.This paper describes the methodology undertaken in detail, and discusses the results obtained.CITATION:Bennett, D and La Rosa, D, 2016. The Frieda River Project – a Novel Approach to Analysing Exploration Drill Core: How Broken is Broken?, in Proceedings The Third AusIMM International Geometallurgy Conference (GeoMet) 2016, pp 65–76 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jun 15, 2016

By P J. Vardon, L A. van Paassen, Y Yao, A F. van Tol

Thin-lift atmospheric fine drying (AFD) is a technique used to dewater mine and oil sand tailings, which utilises both self-weight consolidation and atmospheric evaporation. The disposed layers undergo a cyclic drying and rewetting process due to precipitation and deposition of additional lifts on top of the dried layer. The current research aims to optimise the deposition process via use of a numerical model and realistic atmospheric conditions, including both periods of drying and wetting. The model is based upon water balance and includes large strain considerations. A number of material behaviours are characterised using empirical fitting curves based upon laboratory measurement of material characteristics, including both the shrinkage and water retention curves for drying and rewetting. The model is able to model multiple lifts, simulating field scale and realistic climatic conditions within timescales suitable for engineering practice (eg seconds or minutes). The model has been previously validated against controlled laboratory experiments and utilised to simulate field tests. A series of simulations are presented to illustrate the ability of the model to be used as a practical tool for the optimisation of a tailings deposition strategy.CITATION:Vardon, P J, Yao, Y, van Paassen, L A and van Tol, A F, 2015. The use of a large-strain drying and consolidation model to optimise multilift tailing deposits, in Proceedings Tailings and Mine Waste Management for the 21st Century , pp 263–270 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

The Wattle Dam gold mine, located near Kambalda in the Goldfi elds region of Western Australia has recently progressed to an underground operation and is now believed to be Australia's highest grade operating gold mine. At end of March 2010, the deposit had reserves of 132 000 t @ 20.8 g/t for 88 000 oz and by the end of June 2010 had produced 110 000 oz from open-pit and underground mining. The Wattle Dam main lode is characterised by very coarse gold mineralisation. Gold occurs as cm to decimetre fracture fi ll veinlets, shear surface coatings and erratic fl akey clusters. The gold has no quartz or silica association and lacks adjacent low-grade mineralisation or alteration assemblage. Geologically it appears atypical of Archaean lode gold deposits and may represent an extreme end member of the type. Definition of the lode is largely dependent on effective geological identification of the host lode zone and an understanding of the erratic distribution and grade behaviour of a high-nugget, coarse gold deposit. Dependence on assay data to defi ne the lode zone would result in the deposit being mined incorrectly and much of the deposit being left unexploited. This paper discusses the geology, coarse gold characteristics and defi nition methods which are used to successfully defi ne and mine the deposit.

Aug 1, 2010

By R Wei, Y Peng, D Seaman

This study addresses a widespread problem confronting the mining industry: the deleterious effect of clay minerals in flotation. This problem is seemingly exacerbated by the presence of iron contamination from grinding media. The interaction of clay minerals and grinding media in copper and gold flotation was investigated in this study. A low-clay ore and a high-clay ore were obtained from Telfer to represent different contents of clay minerals, while stainless steel and mild steel grinding rods were used to produce different grinding chemistry, in particular, iron contamination. Flotation tests on an unsized and sized basis were conducted to reveal how clay minerals and grinding media affect copper and gold flotation. Iron contamination and the oxidation of copper minerals were quantified by ethylene diamine-tetra acetic acid (EDTA) extraction. It is interesting to find that both clay minerals and iron contamination depressed the flotation primarily in fine particles smaller than 33 ¦m, and clay minerals played a dominant role. Although flotation of coarser particles greater than 33 ¦m was less affected by clay minerals and iron contamination, coarser grinding to increase P80 was not an effective way to improve copper and gold flotation for the high-clay ore. This study suggests that to improve copper and gold flotation from clay ores, clay dispersion in conjunction with the minimisation of iron contamination may be required.CITATION:Wei, R, Peng, Y and Seaman, D, 2013. The effect of grinding media on copper and gold flotation in the presence of clay minerals, in Proceedings World Gold 2013 , pp 283-288 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By R A. Anand, N N. Viswanathan, M M. Pande

Slags are the most voluminous solid by-products generated in pyrometallurgical operations, and, as such, finding an application for these oxidic materials is pertinent to maintaining resource efficiency. In particular, pyrometallurgical copper production is associated with high slag rates, typically ranging from 2.2 to 3.0 tons of slag per ton produced copper, which necessitates slag valourisation. A possible application for these iron silicate slags is as supplementary cementitious materials (SCMs), which effectively lowers the CO2 emissions per ton of cementitious material. Although utilising iron silicate slags as SCMs has been studied in previous work, the scientific literature has limited data on the effect of composition on the inherent reactivity in cementitious systems. More specifically, no reports on the impact of FeO/SiO2 ratio have been presented in previous publications. Therefore, the present study aimed to isolate this parameter in a synthetic FeO-SiO2-Al2O3-CaO-MgO-Cr2O3 system. Since the amorphous content is a pertinent parameter for SCMs, a high-temperature confocal laser scanning microscope (HT-CLSM) was utilised to assess the crystallisation behaviour at continuous cooling conditions. Furthermore, high-temperature rheological experiments were conducted to measure the viscosities of the slags in relation to the crystallisation behaviour. The experiments showed that depolymerising the slag by increasing the FeO/SiO2 ratio generated a less viscous slag, which showed higher tendencies for crystallisation. Furthermore, experiments assessing the inherent reactivity as an SCM showed that depolymerising the slag by increasing the FeO/SiO2 ratio as the sole independent parameter generated an initially more reactive slag. However, replacing SiO2 with FeO was found to negatively affect the reactivity as measured over seven days within the tested compositional range.

Jun 19, 2024

By R Dunne

"Continuous improvement on metallurgical treatment plants is possible only when good data and analysis of the data are available. Good data implies appropriate and accurate mass measurement coupled with good sampling practices and accurate chemical analysis especially when carrying out monthly metallurgical metal reconciliations. Adequate characterisation of key samples (eg tailings, feed, concentrates and others) at timely intervals is an important part of a good continuous improvement program. The data from this will help identify opportunities to improve operation performance and thus profitability. Examples are provided of projects that have led to improved plant performance based on good metallurgical data collection and analysis.Citation:Dunne, R, 2016. Using Metallurgical Data to Drive Continuous Improvement, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 201–206 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By L Thorburn

In 2009, the Queensland Government developed a series of amendments to environmental authorities (EAs) for mines throughout the Fitzroy Basin in response to studies that assessed the cumulative impacts of mine water discharges in the basin. One of the key amendments was the requirement for all mines in the Fitzroy Basin to develop and implement a receiving environment monitoring program (REMP). The intent of the REMPs was to provide baseline information on the condition of the receiving environments of the mines and any impacts resulting from release of mine-affected water. Since this time, the requirement to complete a REMP has been incorporated into new or revised EAs for mines (including metalliferous mines) in other regions, as well as for other industries that discharge to natural watercourses (such as coal seam gas). This paper discusses the approaches that can be used to incorporate biological monitoring and direct toxicity assessments into REMPs. It highlights the importance of collecting biological data using sound experimental design principles to investigate whether releases resulted in environmental harm; and the use of monitoring data, coupled with direct toxicity assessments, for setting more realistic, site-specific trigger values and release limits (compared to the default guidelines such as Australian and New Zealand Environment and Conservation Council (ANZECC), which may not be appropriate to the region). Implementation of a robust REMP can maximise outcomes for both the proponents and the environment.CITATION:Thorburn, L, 2013. Receiving environment monitoring programs - making the most out of biological indicators and direct toxicity assessments for monitoring of aquatic ecosystems, in Proceedings Water in Mining 2013 , pp 143-148 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 26, 2013

By P Revell, B Adair, D King, L Keeney

Grade Engineering®, integrated across the mine value chain, has a pivotal role to play in achieving step change reductions in energy and water usage in mine operations. High levels of gangue rejection in the mine can significantly improve mineral head grades and overall productivity. A highly successful example is described at the Minera San Cristóbal (MSC) operation. The nature of the mineralisation in their “intrusive” ore domains in particular has facilitated high rejection rates (75 % of the mass), with significant upgrading of metal to the “accepts” streams (equating to a 2.6 times upgrade in the intrinsic Nett Smelter Return). Results from a series of production trials have confirmed these strong upgrades, resulting in the transformation of mineralised “marginal wastes” to high grade ore feedstocks. If new approaches to more energy and water efficient comminution and separation technologies can also realise gangue rejection at finer sizes in the concentrator, then preconcentration strategies across the value chain also offer the promise of no wet tailings treatment facilities and greatly reduced volumes of waste streams. This “No Tails” strategy is discussed, along with the integrated technologies needed to realise its effect. The work suggests a pathway and insights of a sustainable future for the Minerals Industry, unconstrained by Energy and Water, along with no requirement to produce problematic disposal streams. This strategy has the potential to significantly reposition the social, environmental, financial, and regulatory context of existing and new mining opportunities.

Nov 10, 2020

By T Baumgartl, B Richards

The association of specific plants and plant communities with soils developed over underlying superficial orebodies and mineralisation has been long recognised. It has given rise to the use of plant indicators for geobotanical exploration as a regular component of primary minerals reconnaissance where there is an undisturbed vegetation cover. That the chemical composition of indicator plants is a measure of their soil environment has further led to biogeochemical prospecting methods for minerals and its use in the mapping of underlying ore deposits. Where there is a strong surface expression of metal and metalloid anomalies, concentrations of potentially phytotoxic elements may reach a level at which they have strong selective impacts on plant populations. In such circumstances, natural selection has operated in the development of a unique flora composed of plant species and individuals with genetically-based tolerances to the stressed environment in which they continue to survive. These plants are called metallophytes. Metallophytes occur globally on all metalliferous sites, both in pristine undisturbed environments and in areas of mineral workings, ancient and modern. However, the best-developed primary metallophyte vegetation is found in the most ancient areas where there has been a long-term evolutionary impact of the underlying geology through ore weathering and dispersion of metals into the rhizosphere zone. Natural selection of metal-tolerant races of plants in these largely undisturbed areas can eventually lead to speciation and the development of an endemic regional metallophyte flora (Baker et al , 2010). Mineral wastes resulting from mining activities also allow colonisation by metal-tolerant individuals leading to the establishment of metallophyte communities. The distribution and extent of such communities is determined by regional and local factors relating to climate and substrate conditions and the availability of suitable plant resources on which natural selection can operate (Baker, 2009).The ability of metallophytes to tolerate extreme metal concentrations commends them as the optimal choice for ecological restoration of mineral wastes and metal-contaminated sites. Metallophytes have recently also spawned several novel phytotechnologies, including phytoremediation and phytomining (Chaney et al, 2000, 2005; Baker and Whiting, 2008). Action towards conserving the global metallophyte resource base is imperative because many species are under threat of extinction from new and extensive mining activities (Whiting et al, 2004). This has been identified as a priority in the Mining, Minerals and Sustainable Development (MMSD) Project of the Global Mining Initiative in 2002 but positive responses from the minerals industry have been slow. The last decade has, however, seen an ever-increasing interest in metal-tolerant and metal-accumulating plants, both from an academic standpoint and their use in revegetation and phytostabilisation (Tordoff et al, 2000; Baker and Whiting, 2008; Baker, 2009). Few studies have highlighted the need to conserve and develop these unique plants (Whiting et al , 2004). This presentation identifies future research needs for the conservation and exploitation of the global metallophyte biodiversity and its potential in sustainable mine closure. CITATION:Baumgartl, T and Richards, B, 2012. Evaporation and salt transport under variable climatic conditions, in Proceedings Life-of-Mine 2012 , pp 179-186 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

By K Ehrig

You are a geologist, geometallurgist, or metallurgist/process engineer and are fortunate enough to work for an organisation who asks you to design/execute a geometallurgy program. What seems like a simple request is actually not a trivial exercise. æRecipeÆ style manuals are not readily available. However, many æexpertsÆ are lurking around willing to deliver solutions which will solve all of your problems. Even though similar ore deposit styles (e.g. porphyry Cu, IOCG, Ni-laterites, calcrete hosted U, etc.) have many similar characteristics, each ore deposit is unique. Hence your geometallurgy program needs to be æfit-for-purposeÆ. This paper offers some insights gained via designing and executing geometallurgy programs from exploration through to production, and working at a mine where you are held accountable for your metallurgical performance predictors.CITATION:Ehrig, K, 2013. Geometallurgy - What do you really need to know from exploration through to production?, in Proceedings MetPlant 2013 , pp 28-33 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

Triboelectric Separation - Beneficiation of Coal The performance of triboelectric separators is highly sensitive to the selectivity of the particle charging process. This paper presents a quantitative study on triboelectric coal beneficiation. The performance of different charging media was studied. Stainless steel was identified as having a work function between that of coal and silicate gangue and found to be the optimum charging medium for coal beneficiation. Recent results from separation tests were performed where silicate gangue was separated from crude coal using a parallel plate free-fall separator are illustrated.

Sep 13, 2010

By D Kentwell

For deposits where a full assay suite of elements/oxides is available and where several variables are critical to the evaluation of the deposit, it is desirable for the estimated block values of all elements/oxides to sum to 100 per cent of the weight per cent. This is difficult to achieve in practice and the estimation methods used need to be designed to minimise bias of the key elements/oxides by ensuring that block estimates are consistent with the individual assays and that the estimated totals are as close as possible to 100 per cent.This paper presents a case study of two domains within a magnetite hematite deposit, one with a high level of drilling classified as Measured and one with a lower density of drilling classified as Indicated. Several estimation methods were tested to evaluate their ability to maintain consistency of the proportions of each element/oxide and sum to 100 per cent. The following methods were evaluated: ordinary kriging, co-kriging, inverse distance and min/max autocorrelation factors (MAF) all as implemented in the Geovariances Isatis software.The comparisons showed that the MAF method produced the most robust estimates in terms of block totals and that grades and tonnages at the reporting cut-off were not significantly different between methods. At an individual block scale all methods produce artefacts that are less than desirable but can only be remedied by additional drilling.CITATION:Kentwell, D, 2015. Comparison of min/max autocorrelation factors, kriging, co-kriging and inverse distance block totals – a magnetite hematite case study, in Proceedings Iron Ore 2015, pp 465–474 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By the use of flotation tests it was confirmed that there are two functions of oxygen in sulphide mineral flotation. Sized samples of galena and chalcopyrite were sulphidized, washed free of excess sulphide ion, and then contacted with air-saturated water for certain lengths of time. The mineral was then transferred to a sealed laboratory flotation cell containing water with a known concentration of dissolved oxygen. Xanthate and frother were added and flotation continued for 1 min.Both the extent of mineral oxidation and the concentration of dissolved oxygen markedly affected the flotation of galena and chalcopyrite. The response to a change in either variable is dependent on the level of the other, but generally best flotation occurs with the maximum degree of air saturation of the pulp. Galena flotation is hindered by oxidation of the mineral beyond a small threshold amount but a similar effect for chalcopyrite was not observed...

Jan 1, 1967

By D Roughsedge, J van der Sandt, L van den Berg

Axial flow fans are commonly used as auxiliary fans in underground mines to supply air to development headings. As diesel dilution requirements increase the fans used in conjunction with ventilation bags are becoming larger in diameter to move greater quantities of air over greater development distances. It is not uncommon for mining operations to sometimes use a number of these larger auxiliary fans with high airflow capacity in parallel as primary fans for the operations. These primary fan stations are often considered temporary installations and the fan selection and fan station design is rarely optimised. These temporary installations may become permanent resulting in an inefficient or unreliable primary ventilation system. A recent study looked at the likely causes of multiple primary fan failures at one operation with axial fans installed as primary units where the fan selection and fan station aerodynamic design was far from optimal. This paper explores some of the typical mechanisms of failure such as high pressure stall, unbalanced airflow, and fan tip speed as well as fabrication material. The paper proposes a number of good practise principles that should be considered during the design of a fan station. A second topic covered is the advantages and disadvantages of using different types of fans such as axial, mixed flow and centrifugal units. Here the concept of fan specific speed and its relevance to fan selection is discussed. Finally the paper quantifies the effect of using a high pressure auxiliary fan as a primary fan in a low pressure circuit, which may increase the mineÆs operation cost.CITATION:van der Sandt, J, van den Berg, L and Roughsedge, D, 2013. Practical considerations when using auxiliary axial flow fans as a primary mine fan, in Proceedings The Australian Mine Ventilation Conference , pp 63-70 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By S Gillies, H W. Wu

A study has been undertaken into mine ventilation systems currently in use within Australian modern coal longwall (LW) extraction mines. It reviews systems and discusses evolving changes being adopted to address the more complex challenges. There is a strong move to longer panels, wider faces, greater extraction heights, increased production rates, more efficient ventilation and decreased personnel. Each of these changes is motivated by improvement in productivity and generally leads to cost reduction. In addition, mine workings are moving deeper, which results in increased ventilation control issues such as higher total and respirable dust levels, greater seam gas contents in parallel with lower in situ permeabilities, spontaneous combustion and heat management issues. A comprehensive database of Australian LW ventilation practice is analysed. Currently there are a variety of LW panel ventilation circuits used in Australian underground coal mines due to various combinations of seam characteristics, gas emission rates, spontaneous combustion, geological features and surface constraints. The main issues usually addressed in the designing and planning of ventilation circuits for LW panels are airway velocity, gas concentrations, LW cutting methods (eg Bi-di, Uni-di or half web), ventilation of control devices, pressure differentials and leakage paths and understanding gas concentrations across the length and width of the goaf. If the ventilation circuit can manage the applied contaminant load (gases, heat and dust) at an acceptable cost and circuit duty, then supplementary controls, such as gas drainage, refrigeration and dust sprays and scrubbers, may not be required. CITATION:Gillies, S and Wu, H W, 2013. Review of Australian longwall panel ventilation practices, in Proceedings The Australian Mine Ventilation Conference , pp 87-94 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By P Ottenio, B CarrT

In the last 40 years, the froth flotation process widely spread in the paper industry becoming the dominant technology for ink removal from recovered paper slurries and cellulose fibres recovery. Most of current models used to describe the flotation deinking process are based on hydrodynamic and statistical theories of ink particles collision/attachment to air bubbles. The complexity of these theoretical models, together with the variability of the recovered papers composition, does not allow to define a set of æeasy to handleÆ equations to be used for modelling industrial flotation cells. This main limiting aspect makes that, in several deinking process modelling tools, basic parameters used to characterise the flotation unit, ie yield, ink removal efficiency, water loss, are constant parameters. Although in some process simulation tools the flotation yield/efficiency is adapted to process control parameters (air ratio, pulp flow, pulp consistency), physicochemical variables (namely the pulp frothing aptitude, the pulp surface tension and the ink adhesion energy to air bubbles) are not taken into account to adjust the flotation yield/efficiency. Data collected during recent laboratory and pilot plant experiments focusing on the role of surface active substances on the flotation efficiency were therefore interpreted and used to identify general trends that could be described with simple semi-empirical models. A set of model equations using surface tension and froth removal height as main variables was then defined in order to describe the behaviour of a pilot flotation cell. Trends obtained during the dynamic simulation of the deinking pilot plant were in good agreement with experimental data obtained under similar experimental conditions, thus indicating that developed equations can forecast with good approximation the behaviour of a flotation deinking unit.

Jan 1, 2005

By M A. Rhamdhani, K Avarmaa, A Putera, J Chen, G Brooks

Silicon-based photovoltaic cells are currently the most dominant types applied to convert solar energy to electricity. In solar-grade silicon (SG-Si), the control of boron (B) and phosphorus (P) is very critical. Generally, these elements are difficult to remove into acceptable sub-ppm levels from lower grade Si. This study investigates slag treatment as a process for Si refining, focusing on the behaviour of P and B. The experiments were conducted by equilibrating Si-B-P alloys with 43 wt per cent SiO2 – 47 wt per cent CaO – 10 wt per cent Al2O3 slag under inert atmosphere at 1500°C. Different crucible materials were used (Al2O3, SiO2 and MgO), which determined the primary saturation phase for the system and modified the final slag composition accordingly. The samples were equilibrated and analysed with microanalysis techniques (EPMA (electron probe microanalysis) and LA-ICP-MS (laser ablation inductively coupled plasma mass spectrometry)). New standards were prepared and applied in the LA-ICP-MS analyses. Experimental results show that silver is essentially fully dissolved in silicon, as well as most phosphorus with LP ( = wt per cent P in slag/wt per cent P in Si) between 0.1–0.3. The distribution coefficient of boron was measured to be between 1 and 2. The crucible material used had an influence on the phase compositions and slight influence on the distribution coefficients of boron and phosphorus. The experimental results provided new accurate data when considering applicability of slag treatment as a technique for Si refining and Si PV cell recycling.

Jun 19, 2024